Washing machines, such as clothes washers, refreshers, and non-aqueous systems, have a treating chamber, which may have a configuration of a rotating wash basket, in which laundry items are placed for treating according to a cycle of operation. The wash basket may be perforated, and may be surrounded by an imperforate tub having a sump. A liquid supply and/or recirculation system supplies liquid to the washing machine to a desired fill level in the tub. The laundry treating appliance may further have a controller communicably and operably connected with the various components of the appliance for controlling the appliance to execute the cycle of operation.
The liquid supply and recirculation system may include an air trap and a pressure sensor used to control the fill level in the tub. A typical air trap includes the pressure sensor fluidly coupled to one end of a conduit, which can include a tube or hose, the opposite end of which is open and in communication with the sump. The pressure sensor may be coupled to the controller. As liquid enters the tub, water will enter the open end of the conduit, and, as the liquid level rises, increase the air pressure in the conduit. When the air pressure reaches a predetermined value which correlates to a certain fill level, as determined by the pressure sensor, filling is ceased.
After the completion of a cycle of operation, there may still be moisture within the washing machine, such as wash basket or tub, including the sump. If the washing machine is moved from its normal operating orientation, e.g. if the washing machine is tilted from vertical, residual moisture can enter the air trap. The residual moisture can become trapped, such as by capillary action, in the conduit leading to the pressure sensor, causing negative pressure at the pressure sensor, resulting in erroneous readings from the pressure sensor, which results in improper water levels.
Air trap failure due to residual moisture can even be a problem for new washing machines. Washing machines are often tested prior to shipment by conducting a cycle of operation, which can leave residual moisture within the washing machine. If the washing machine is shipped in a horizontal position, the residual moisture may enter the air trap, leading to failure. During shipping, a washing machine may experience extreme temperature variation. The volume of air within the air trap may expand and/or contract as the temperature increases or decreases during shipping. This expansion/contraction may produce a pumping effect of the residual moisture within the washing machine left over from testing done prior to shipping. This pumping effect may be enough for the water to reach the hose, and water may become trapped in the hose by capillary effect, resulting in erroneous readings from the pressure sensor even after washing machine is places in its normal operation orientation. These problems prevent shipment of washing machines in a horizontal position. Even if washing machines are not shipped horizontally, some washing machines are assembled with a pedestal once they arrive in a household, which requires that the washing machines be tilted from vertical.